The use of soapy water and freezing as secondary steps for euthanasia in cave (Blaberus giganteus) and Madagascar hissing (Gromphadorhina portentosa) cockroaches.

Abstract

To evaluate methods for euthanizing cave cockroaches (CCs; Blaberus giganteus) and Madagascar hissing cockroaches (MHCs; Gromphadorhina portentosa). It was hypothesized that both suggested methods would be effective for humane mass euthanasia of both species. Approximately 800 CC. The CCs were separated into replicate groups of 25, 50, 75, 100, and 150 grams and placed into 3.8-L plastic bags. Twenty-seven MHCs were divided into groups of 2 to 3. The study took place from January to March 2023. All CC groups were exposed to 100% carbon dioxide (CO2) at a rate of 4 L/min until the bag was full. Madagascar hissing cockroaches were similarly anesthetized using either CO2 or 2 mL of isoflurane on a cotton ball in a 1-L container or a combination of CO2 and isoflurane. Once cockroaches were immobile, secondary euthanasia steps were performed. One bag of CCs per weight category was exposed to soapy water (5% Dawn dishwashing liquid), and the second was placed into a -80 °C freezer. The containers of MHCs were evenly exposed to the 2 euthanasia methods. Individuals remained in their secondary euthanasia method for 30 minutes. Regardless of the weight of the CCs within each bag, there was no impact on time (1.8 ± 0.4 minutes [mean ± SD]) to immobility. The failure rates for both species were 0.2% CI (-0.1% to 1.5% [1/413]) for soapy water and 0.5% CI (0.005% to 1.9% [2/414]) for the freezer method. These results support the use of both 2-step euthanasia methods in CCs and MHCs. These methods will serve as an evidence-based alternative for humane mass euthanasia in cockroaches.